Build a synastry form

I would like to make a "synastry" form, so the visitor has to choose one option from the first dropdown menu and one from the second dropdown menu. e.g Scorpio (1st) - Aries (2nd). When the visitor clicks on "Submit" button he will have to see the post which refers to "Scorpio/Aries" or "Aries/Scorpio". Preferred implementation in Formidable Forms